[2.0.x] Add pin configuration for Fysetc F6 (#11932)

Marlin/src/pins/pins.h

@@ -152,6 +152,8 @@
   #include "pins_RAMPS_ENDER_4.h"     // ATmega2560                                 env:megaatmega2560
 #elif MB(GT2560_V3)
   #include "pins_GT2560_V3.h"         // ATmega2560                                 env:megaatmega2560
+#elif MB(FYSETC_F6_13)
+  #include "pins_FYSETC_F6_13.h"      // ATmega2560                                 env:megaatmega2560
 
 //
 // Other ATmega1280, ATmega2560